Various systems have been developed using databases along with the development of the information industry in recent years. In a storage apparatus for storing databases, communication between a host system such as a so-called open system or mainframe, and storage devices such as hard disk drives is performed via a controller having a cache, a processor, and interfaces with the host system and the storage device.
Each interface unit for performing communication with the host system and the storage devices have been fixed on a side of the controller. Recently, there is a technology in capable of flexibly changing the input/output (hereinafter, sometimes called “I/O”) configuration in the storage apparatus with the arrangement to modulize these interface units and configure the modulized interface units being mountable and dismountable to the controller (see Non-Patent Literature 1).
As an example of such module configuration mountable and dismountable to the controller, there is a configuration in which I/O modules and a controller body are connected to each other and which enables connection of various kinds of I/O modules by adopting, for example, PCI-Express for connecting the I/O modules. A storage apparatus capable of flexibly adding or changing an interface unit by inserting or removing I/O modules, using the above-described technique, has been provided (see Patent Literature 1).